Alloy of refractory metals and process of forming same



UNHTEE STATES JOHN ADAM YUNCK, OF SOUTH ORANGE, NEW JERSEY.

ALLOY OF REFRACTORY METALS AND PROCESS OF FORMING SAME.

No Drawing. Application filed January 17, 1913, Serial No. 742,711.Renewed July 14, 1921.

Specification of Letters Patent.

Serial To all whom it may cmwem:

Be it known that 1, JOHN A. YUNoK, a citizen of the United States ofAmerica, residing at South Orange, county of Essex, State of New Jersey,have invented certain new and useful Improvements in Alloy of RefractoryMetals and Processes of Forming Same, of which the following is aspecification.

My invention relates to an alloy of tungsten and thorium particularlyuseful in making metal filaments for incandescent lamps, and a method ofmaking same. Various alloys of the refractory metals have been proposedfor this purpose because the alloys are usually more ductile than theirconstituents taken separately, but none of such alloys heretoforeproposed have been successful for the purpose because they either hadtoo low a fusing point, or volatilized at high temperatures'anddiscolored the lamp bulb.

I have discovered that an alloy of tungsten, 95 to 99 parts, andthorium, 5 to 1 fparts, can be swaged and drawn down to lament size, andproduces a filament of high eificiency, high melting point and one whichdoes not discolor the lamp bulb. In making such alloy I employ thefollowing process:

I dissolve from 1 to 5 parts by weight of thorium nitrate in distilledwater and mix into a thick paste with from 99 to 95 parts of powderedtungsten oxide, or equivalent compound of tungsten, or with purepowdered tungsten. This paste is dried and heated until the moisture isdriven off, then crushed to powder, put into a crucible and fired foreight hours. The temperature is gradually raised to about 1200 degreescentigrade, maintained-for about three hours at that point, and thengradually lowered. When the crucible and contents are reduced toatmospheric temperature, which usually does not occur until about 20hours after the beginning of the firing, the contents are taken out,ground and sifted through bolting cloth.

The fine material which has passed through the bolting cloth is thenpreferably placed in a nickel tube of say about 2 inches internaldiameter and rovided with connections for passing by rogen gas throughto cool gradually, this entire portion of the process usually consumingabout seven hours time. During the entire period a current of hydrogengas is kept flowing through the tube, over the powdered mixture.

After the material has been treated as above described it is againsieved or bolted and the fine powder resulting from this operation ismixed with any suitable binder and squirted from a mold to form a rod.These rods I place in a suitable receptacle, of highly refractorymaterial, which is placed in an oven where it is gradually raised to atemperature of about 1200 degrees centigrade, maintained there for aboutan hour and a half and then gradually cooled off. A stream of hydrogengas is continually passed through the oven in contact with the materialduring this operation.

The rod so formed and baked is next sintered by placing it in a treatingbottle through which a supply of dry hydrogen gas is continually flowingand subjecting it to the passage of an electric current of about thefollowing strength:

Amperes. First five minutes 500 Second five minutes 750 Third fiveminutes 1000 Next ten minutes 1500 Last five minutes 2000 The current isthen gradually turned off reducin it to zero in about 5 minutes. As at,present advised, I believe the fact that both constituents of the alloyare liberated from their respective compounds during the formation ofthe alloy, so that they may combine while in the nascent condition soresulting, has an important efl ect on the perfection of the alloyingaction, and on the durability of the product under the conditions of itsuse.

The sintered ingot thus produced may be worked down to filament form byknown processes. a

"The filament so produced is tough and can be safely handled in makinglamps, is of practically the same efficiency as pure tungsten, has ahigh melting point and will not volatilize and blacken the lamp bulbwhen run at high incandescence.

Having, therefore, described my invention, I claim:

1: An alloy for use in making metal filaments and the like, composed ofat least 95 per cent of metallic tungsten and the rest pure thorium. v

2. The product of the invention herein set forth, being an alloy of morethan 95 per cent tungsten and less than 5 per cent thorium. I I

3. As a step in the herein described process offorming alloys oftungsten and thorium, heating a mixture of a finely powdered oxide oftungsten and thorium nitrate in such manner as to entirely reduce thethorium nitrate.

4. The process of forming an alloy of tungsten and thorium whichconsists in mix in an'oxide of tungsten and thorium nitrate, reducingthe mixture to a fine powder, subjecting the powder to high heat for aperiod of hours in a non-reducing atmosphere, regrinding and subjectingthe powder for several hours in a reducing atmosphere to heat suflicientto reduce the compounds forming said powder, then mixing said powderwith a suitable binder, forming into rods or wire, and heating andsintering the same.

5. The method which consists in drying tungstic oxide uniformlymoistened with a thorium salt solution, pulverizing the dry residue,heating said .ulverized residue to convert all sald thorlum salt tothorium oxide, and completely reducing said residue by maintaining it atthe highest possible temperature-in a dry reducing atmosphere for aprolonged period until the last trace of 'oxide is removed and a ductilealloy is proof oxide.

JOHN ADAM YUNCK. Witnesses:

A. PARKER SMITH, M. G. CRAWFORD.

